This invention relates to the processing of liquid products and to the detection of microorganisms which may be present in the liquid product during processing. More specifically, the invention relates to the continuous sampling of a liquid product during processing so that the detection of microorganisms in the sample may be readily correlated to a specific suspect batch of bottled product, which may then be isolated from uncontaminated batches of the bottled product.
In conventional liquid product processing lines in which the bottled product, for example any consumable product or drug, must be free of microorganisms, such as bacteria and yeast, microfiltration of microorganisms in the product flowing in the processing line occurs generally between the product supply station and the bottling station. The integrity of the microfiltration system is periodically examined by taking discrete random samples of the product which is flowing between the microfiltration system and the bottling station.
These liquid product samples are passed through sterile membranes which filter out microorganisms. The membranes are then introduced to a nutrient medium and incubated for a period of time. If the membrane has filtered out microorganisms the subsequent incubation of the membranes on the nutrient medium will result in a growth of microorganism colonies which are visible, either microscopically or to the naked eye.
The time required for the visual detection of microorganism colonies depends upon the particular microorganism and may vary from 24 to 96 hours. Detection of "micro" colonies may be possible within 18 hours by use of a microscope. In a modified but generally less accurate method, the detection of microorganisms can occur much faster by taking advantage of the enzyme activity of living cells. By treating or staining the membrane with a fluorescein-containing substance, free fluorescein will accumulate in living cells as a result of esterase activity, rendering the cells fluorescent when viewed under light of a specific wavelength. The detection of microorganisms in the sampled product in either of the above methods permits holding the bottled product for inspection.
More recently, continuous in-line sampling of the liquid product flowing in a processing line has been accomplished by diverting a portion of the liquid flowing between the microfiltration system and the bottling station through a container which houses a sterile membrane. A portion of the liquid product flowing to the bottling station is diverted through the membrane for a specific period of time, usually several hours. The diverted flow is then stopped, the container removed and the membrane placed in a nutrient medium where incubation will possibly result in the detection of microorganism colonies.
This more recent sampling method has several inherent disadvantages. In high speed bottling lines, such as are now common in the wine industry, the detection of microorganisms by such a method requires that large amounts of the finished bottled product be held for examination, since it is not possible to specifically isolate those bottles which may be contaminated with microorganisms. Additionally, since contamination of the liquid product frequently occurs when the supply tanks and the microfiltration systems are periodically changed, i.e., during periods when no liquid product is flowing to the bottling station, it is not possible to sample the liquid product during such periods.